fix(webview): 文件选择器权限检查 + content URI 本地缓存

1. 触发文件选择前检查存储读取权限：API < 33 检查
   READ_EXTERNAL_STORAGE，API 33+ 按 MIME 类型检查粒度媒体权限；
   权限不足时先申请，结果回调后再启动选择器。

2. 将选中文件的 content:// URI 复制到 app 私有缓存目录后再传给
   WebView，解决云盘、系统相册、媒体库等 content://media/ URI
   WebView 渲染进程无法读取导致 H5 上传内容为空的问题。
   同时修复了 doc/docx 无响应及 PDF 返回不可用 URI 的问题。

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sdk-webview/src/main/java/com/xuqm/sdk/webview/XWebViewView.kt

@@ -9,6 +9,7 @@ import android.net.Uri
 import android.os.Build
 import android.os.Handler
 import android.os.Looper
+import android.provider.OpenableColumns
 import android.util.Base64
 import android.view.ViewGroup
 import android.webkit.JavascriptInterface
@@ -219,6 +220,69 @@ internal fun String.escapeJs(): String = replace("\\", "\\\\")
     .replace("\n", "\\n")
     .replace("\r", "\\r")
 
+/**
+ * Returns the storage permissions that should be requested before showing the file picker.
+ * - API 33+: granular media permissions keyed to the accepted MIME types
+ * - API < 33: READ_EXTERNAL_STORAGE
+ */
+internal fun requiredStoragePermissions(acceptMimes: Array<String>): Array<String> {
+    return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+        buildList {
+            val any = acceptMimes.any { it == "*/*" }
+            if (any || acceptMimes.any { it.startsWith("image/") }) add(Manifest.permission.READ_MEDIA_IMAGES)
+            if (any || acceptMimes.any { it.startsWith("video/") }) add(Manifest.permission.READ_MEDIA_VIDEO)
+            if (any || acceptMimes.any { it.startsWith("audio/") }) add(Manifest.permission.READ_MEDIA_AUDIO)
+        }.toTypedArray()
+    } else {
+        arrayOf(Manifest.permission.READ_EXTERNAL_STORAGE)
+    }
+}
+
+internal fun storagePermissionsGranted(context: Context, acceptMimes: Array<String>): Boolean =
+    requiredStoragePermissions(acceptMimes).all {
+        ContextCompat.checkSelfPermission(context, it) == PackageManager.PERMISSION_GRANTED
+    }
+
+/**
+ * Copies the content pointed to by [uri] into a stable local cache file so that WebView's
+ * file-chooser callback can read it regardless of where the file was picked from.
+ *
+ * Cloud/media provider URIs (Google Drive, Photos, OPPO Gallery, etc.) are only readable
+ * by the app process that received the picker result; some break if the WebView chromium
+ * renderer tries to open them later. Returning a plain file:// URI from the app's cache
+ * dir avoids the problem entirely.
+ *
+ * Returns null if the stream cannot be opened (caller should fall back to the original URI).
+ */
+internal fun copyUriToWebViewCache(context: Context, uri: Uri, mimeType: String?): Uri? {
+    return runCatching {
+        val displayName = context.contentResolver.query(
+            uri, arrayOf(OpenableColumns.DISPLAY_NAME), null, null, null
+        )?.use { cursor -> if (cursor.moveToFirst()) cursor.getString(0) else null }
+
+        val ext = mimeType?.let { MimeTypeMap.getSingleton().getExtensionFromMimeType(it) }
+            ?: displayName?.substringAfterLast('.', "").takeIf { !it.isNullOrBlank() }
+            ?: "bin"
+        val base = displayName?.substringBeforeLast('.')
+            ?.replace(Regex("[^a-zA-Z0-9_\\-]"), "_")
+            ?.take(64)
+            ?: "upload"
+
+        val dir = File(context.cacheDir, "webview_uploads").also { it.mkdirs() }
+        val dest = File(dir, "${base}_${System.currentTimeMillis()}.$ext")
+
+        val bytesRead = context.contentResolver.openInputStream(uri)?.use { input ->
+            dest.outputStream().use { out -> input.copyTo(out) }
+        } ?: return null   // openInputStream returned null — URI unreadable
+
+        android.util.Log.d("XWV", "copyUriToWebViewCache: $uri → ${dest.name} ($bytesRead bytes)")
+        Uri.fromFile(dest)
+    }.getOrElse { e ->
+        android.util.Log.w("XWV", "copyUriToWebViewCache failed for $uri: ${e.message}")
+        null
+    }
+}
+
 @SuppressLint("SetJavaScriptEnabled")
 @Composable
 fun XWebViewView(
@@ -361,6 +425,8 @@ fun XWebViewView(
     val pendingFileCallback = remember { mutableStateOf<ValueCallback<Array<Uri>>?>(null) }
     val pendingCameraUri = remember { mutableStateOf<Uri?>(null) }
     val pendingAcceptMimes = remember { mutableStateOf<Array<String>?>(null) }
+    // Mimes saved while waiting for storage permission; launcher fires the picker once granted/denied.
+    val pendingPickerMimes = remember { mutableStateOf<Array<String>?>(null) }
 
     val takePictureLauncher = rememberLauncherForActivityResult(
         ActivityResultContracts.TakePicture()
@@ -385,7 +451,7 @@ fun XWebViewView(
         // crash. We accept the file only when its MIME type matches, or fall back to passing
         // it through when we can't determine the type (to avoid blocking legitimate uploads).
         val acceptedMimes = pendingAcceptMimes.value
-        val actualMime = uri.let { context.contentResolver.getType(it) }
+        val actualMime = context.contentResolver.getType(uri)
         val allowed = acceptedMimes.isNullOrEmpty() ||
             acceptedMimes.any { accepted ->
                 accepted == "*/*" ||
@@ -394,9 +460,31 @@ fun XWebViewView(
         if (!allowed) {
             android.util.Log.w("XWV", "Rejected file: actualMime=$actualMime not in accepted=$acceptedMimes")
             cb?.onReceiveValue(null)
-        } else {
+            return@rememberLauncherForActivityResult
-            cb?.onReceiveValue(arrayOf(uri))
         }
+        // Copy the file content to a local cache file before handing it to WebView.
+        // URIs from cloud providers (Google Drive, Photos, manufacturer gallery apps) and from
+        // media:// content URIs are NOT directly readable by the WebView renderer process.
+        // WebView internally calls ContentResolver.openInputStream(uri) in the main process;
+        // for cloud-backed or access-restricted URIs this silently returns empty content.
+        // Copying to a file:// URI in the app's private cache guarantees WebView can always
+        // read the bytes, regardless of where the file was originally picked from.
+        coroutineScope.launch(Dispatchers.IO) {
+            val localUri = copyUriToWebViewCache(context, uri, actualMime) ?: uri
+            withContext(Dispatchers.Main) {
+                cb?.onReceiveValue(arrayOf(localUri))
+            }
+        }
+    }
+
+    // Storage read permission launcher (READ_EXTERNAL_STORAGE on API < 33; granular media on 33+).
+    // Always fires the picker after the result — if the user denied, SAF still shows accessible files.
+    val storageReadPermissionLauncher = rememberLauncherForActivityResult(
+        ActivityResultContracts.RequestMultiplePermissions()
+    ) { _ ->
+        val mimes = pendingPickerMimes.value ?: return@rememberLauncherForActivityResult
+        pendingPickerMimes.value = null
+        pickContentLauncher.launch(mimes)
     }
 
     val shouldLaunchCamera = remember { mutableStateOf(false) }
@@ -499,6 +587,17 @@ fun XWebViewView(
         onDispose { lifecycleOwner.lifecycle.removeObserver(observer) }
     }
 
+    // Checks storage permissions before launching the file picker.
+    // Requests missing permissions on first use; launches the picker after the result either way.
+    val launchPickerWithPermission: (Array<String>) -> Unit = { mimes ->
+        if (storagePermissionsGranted(context, mimes)) {
+            pickContentLauncher.launch(mimes)
+        } else {
+            pendingPickerMimes.value = mimes
+            storageReadPermissionLauncher.launch(requiredStoragePermissions(mimes))
+        }
+    }
+
     val launchCamera: () -> Unit = {
         if (ContextCompat.checkSelfPermission(context, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
             runCatching {
@@ -635,7 +734,7 @@ fun XWebViewView(
                         when {
                             isCameraCapture -> launchCamera()
                             isImageOnly -> showImageSourceDialog = true
-                            else -> pickContentLauncher.launch(acceptMimes)
+                            else -> launchPickerWithPermission(acceptMimes)
                         }
                         return true
                     }
@@ -700,7 +799,7 @@ fun XWebViewView(
             confirmButton = {
                 TextButton(onClick = {
                     showImageSourceDialog = false
-                    pickContentLauncher.launch(arrayOf("image/*"))
+                    launchPickerWithPermission(arrayOf("image/*"))
                 }) { Text("从相册选择") }
             },
             dismissButton = {